Comprehensive Income - Other Comprehensive Income (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other comprehensive income (loss), before tax	$ 30	$ 896	$ 8,201	$ 6,479
Other comprehensive income (loss), tax	(7)	(228)	(2,097)	(1,648)
Other Comprehensive Income	23	668	6,104	4,831
Unrealized Gains and Losses on Available for Sale Securities
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other comprehensive income (loss), before tax	(397)	668	7,823	5,796
Other comprehensive income (loss), tax	101	(169)	(2,000)	(1,473)
Other Comprehensive Income	(296)	499	5,823	4,323
Unrealized Loss on Cash Flow Swap
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other comprehensive income (loss), before tax	317		48
Other comprehensive income (loss), tax	(79)		(11)
Other Comprehensive Income	238	0	37	0
Amortization of Net Retirement Plan Actuarial Gain (Loss)
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other comprehensive income (loss), before tax	57	172	171	514
Other comprehensive income (loss), tax	(15)	(45)	(44)	(133)
Other Comprehensive Income	42	127	127	381
Amortization of Defined Benefit Pension, Prior-Service Costs
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other comprehensive income (loss), before tax	53	56	159	169
Other comprehensive income (loss), tax	(14)	(14)	(42)	(42)
Other Comprehensive Income	$ 39	$ 42	$ 117	$ 127